The United Arab Emirates, a key member of the Saudi-led coalition fighting in Yemen, is scaling back its military presence there as worsening U.S.-Iran tensions threaten security closer to home, four western diplomatic sources said.

The UAE has pulled some troops from the southern port of Aden and Yemen’s western coast, two of the diplomats said, areas where the Gulf state has built up and armed local forces who are leading the battle against the Iran-aligned Houthi group along the Red Sea coast.

Three of the diplomats said Abu Dhabi preferred to have its forces and equipment on hand should tension between the United States and Iran escalate further after attacks on oil tankers in the Gulf and Tehran’s downing of a U.S. unmanned drone.

“It is true that there have been some troop movements ... but it is not a redeployment from Yemen,” a senior Emirati official told Reuters, adding that the UAE remains fully committed to the military coalition and “will not leave a vacuum” in Yemen.

The official would not provide details on the movements, the numbers involved or specify whether it was happening inside or outside Yemen, where the alliance intervened in 2015 to try to restore the government ousted from power by the Houthis.

It is not clear how many Emirati forces are in Yemen. One Western diplomat said the UAE withdrew “a lot” of forces from the Arabian Peninsula nation over the last three weeks.

Asked whether tensions with Iran were behind the move, the Emirati official said the decision was more related to a holding ceasefire in Yemen’s main port city of Hodeidah, now held by the Houthis, under a U.N.-led peace pact reached last December.

“This is a natural progression,” the official said, reiterating the UAE’s support for U.N. efforts to implement the deal in Hodeidah, a lifeline for millions of Yemenis, to pave the way for talks to end the war.

Hodeidah became the focus of the war last year when the Western-backed, Sunni Muslim coalition tried to seize the port, the Houthis’ main supply line. Under the Stockholm deal, which has yet to be fully implemented, both the Houthis and pro-coalition Yemeni forces would withdraw from Hodeidah.

TANKER ATTACKS

Two of the diplomats said progress on Hodeidah made it easier for the UAE to scale back its presence in Yemen to reinforce defenses at home in the wake of attacks on four oil tankers off the UAE coast in May that was followed by strikes on two more vessels in the Gulf of Oman a few weeks later.

A spokesman for the Saudi-led coalition did not immediately respond to a request for comment.

Washington and Riyadh have publicly blamed Iran for the explosive blasts, a charge Tehran denies. A UAE investigation said a state actor was behind the attacks, which have not been claimed by anyone, but Abu Dhabi has not named any country.

Washington is in talks with allies for a global coalition to protect vital oil shipping lanes in and near the Strait of Hormuz and the subject was broached during a visit by Secretary of State Mike Pompeo to Saudi Arabia and the UAE last week.

In his meeting with Abu Dhabi Crown Prince Mohammed bin Zayed al-Nahyan, Pompeo pressed him on increased maritime security. “We’ll need you all to participate, your military folks,” he said.

The UAE has a smaller army compared to bigger regional allies like Egypt and Saudi Arabia. It has around 63,000 active military personnel, 435 tanks and 137 warplanes, the International Institute for Strategic Studies said in a report released this year.

The UAE has called for de-escalation of tensions in the region which have raised concerns about a direct military confrontation that could spark a war in the region.

The Houthis have stepped up missile and drone attacks on Saudi cities, further fuelling tensions. The group denies being a puppet of Iran and says its revolution is against corruption.

Diplomats said if needed the UAE can always send troops back to Yemen, where Abu Dhabi has built strong local allies with tens of thousands of fighters among southern separatists and coastal plains fighters.

The Yemen conflict, which has killed tens of thousands of people and pushed the country to the verge of starvation, is largely seen as a proxy war between Saudi and Iran.